Bad stumble - what should i log

[Tracyrr]

Newb here so any help would be much appreciated. The car is a 2003 twin turbo corvette. My issue is a really bad stumble or cutout when fully warmed up before any boost is built, it has not done it when the engine is cool or just started. The stumble occurs at part throttle (1/3 to 1/2) in any gear when fully warmed up. Fuel pressure holds steady. My question is what should i log to track down this issue? The car runs well otherwise and btw, it is an SD tune. I will try to attach my tune. Thanks tracy

[Tracyrr]

I am starting to check the obvious things like throttle position and fuel pressure. One thing i just noticed was when it cutout or stumbled real bad, the timing went full advance immediately after it cutout.

[joecar]

Start with these:

Include these engine pids:
VSS
TP or whatever works for ETC
RPM
DYNCYLAIR or DYNCYLAIR_DMA
DYNAIR
MAF (SAE or GM)
MAP (SAE)
IAT
ECT
EQIVRATIO or AFR
SPARKADV
KR
LONGFT1
LONGFT2

[Tracyrr]

ok, i'll add these pids. I will update with more info hopefully. Thanks joe!

[Tracyrr]

***Nevermind, i just found it, thanks****

Looks like i need to add some fuel while under boost... this has nothing to do with the stumble but how do i add fuel. I watched my tuner do it a couple times but i can't seem to find the chart that he would modify fuel. Could someone point me to the fuel chart for kpa over 105? My tune is attached above. Thanks

[joecar]

A0009 Boost VE table

increasing cells in this table increases cylinder airmass which causes increased fuelmass (in order to deliver the commanded AFR/EQ).

[Tracyrr]

Great, thanks joe!

[Tracyrr]

How do i increase my boost VE table kp? It is currently set to 285 max kpa, i need more boost. Thanks

[joecar]

285kPa is the maxiumum on table A0009's axis... when you hit the 285kPa column, the cell values carry on into higher kPa.

[Tracyrr]

So that means i can't view past 285 kpa in A0009? I would like to be able to tune further. Thanks joe!

[joecar]

Table A0009 doesn't go past 285kPa.

[Tracyrr]

Ok, thanks!

[Mr. P.]

How do i increase my boost VE table kp? It is currently set to 285 max kpa, i need more boost. Thanks

:shock: You're making over 25-psi boost?!

Mr. P. :)

[Tracyrr]

I run about 14 - 18 pounds on the street with pump gas/meth but i'm about to go race the car and hope to be in the mid 20's+ with C16. Great forum, thanks!

[Tracyrr]

I was able to capture the stumble on my log. Excuse the length of log but it occurs at frame 7318 and 7519. I also have plenty useless PID's, i have not been able to find boost psi yet..... AFR's go real lean and rpm's drop off, basically the engine stops running for a second. I can manipulate the throttle to keep it running though. p.s... a buddy told me to make sure the 105kpa values equal my 105 kpa values in the VE boost table and they do not equal....not even close actually.... is this my problem? Thanks for any help. 11500

[Tracyrr]

My buddy was right! The 105+ kpa on the boosted ve table was much leaner than the 105kpa on the non boosted ve table which caused a major lean issue on tip-in. Hopefully this will help some newby down the road. Great forum and thanks for the help! tracy